202 
[October 
times the tip of tarsal joints 1—4 is brown, sometimes only the tip of 
3 and 4 or of 4 only. bth. In two of my 9 Umhata the wings are yel¬ 
lowish ; in one they are subhyaline with a slight smoky tinge, as they 
also are in my 5 % . Qth. The intermediate seta generally shrinks in 
drying and is not reliable. Sometimes in the dried specimen it can 
scarcely be distinguished, but in the living insect it is always easily 
seen by the naked eye. 
I believe that in hilineata and Umhata the terminal i of the seta 
of the % 9 imago is always pilose under the lens—a thing which I have 
not noticed in the imago of any other Ephemerinous group but my 
Baetis § A, and there only in the extreme tip. This is also stated by Dr. 
Hagen as a character of the 9 of his second group, with a query that 
the 9 remains in the subimago state like the first group. In that case 
the seta would probably be hairy, not merely at the tip but throughout 
its length. Has the % also of this second group a seta hairy at the tip, 
like the % of Hexagenia. n. g., the sixth group ? 
On the whole, I am satisfied that at Rock Island we have only two 
species of this group— hilineata and Umhata. —the former of which 
occurs in prodigious swarms and only on the banks of the Mississippi, 
in the middle of July; the latter occurs very sparsely and often as 
much as a mile from the nearest river. I found the former in similar 
profusion on the Ohio river in South Illinois, in the middle and latter 
end of July, 1861, so that I suspect it is confined to large rapid rivers. 
It is possible that some of Dr. Hagen’s specimens may belong to a 
third species, with which I am unacquainted. Foreign entomologists, 
who can only study N. A. Ephemerina in the dried specimen, labor 
under great disadvantages, not only because the setae of the specimens 
which reach them are frequently mutilated, or badly shrivelled, but 
because one of the best and most constant characters, the color of the 
eyes, is entirely obliterated in death, to say nothing of the great difl&- 
culty of ascertaining from the generally shrivelled eyes of the dried 
specimen whether these organs are single or double. 
Note 19, p. 177. Every spring many acres of log-rafts are floated 
down to the Rock Island saw-mills from the pineries in Wisconsan and 
Minnesota. Amongst the floating rubbish that accumulates between the 
logs breed myriads of Ephemerinous pupae, which may be often noticed 
crawling out on to the logs to assume the subimago state. As these 
